1.1. What ecological properties of reefs can we measure using remote sensing (Table 1)?
Optical remote sensing methods typically penetrate clear waters to approximately 15–30 m. Light penetration is wavelength dependent, being greater in blue wavelengths (400 nm) than, say, red wavelengths (600 nm). The precise degree of penetration in a spectral band will depend upon the optical properties of the water (e.g. the concentration of coloured dissolved organic matter and suspended sediments). However, a number of workers have capitalised upon the wavelength-dependency of light penetration and proposed methods for predicting bathymetry (e.g. Jupp, 1988; Stumpf et al., 2003). The most recent methods (Stumpf et al., 2003) can be derived from many types of optical imagery (e.g. IKONOS) and accurately reveal patterns of bathymetry on coral reefs to a depth of ≈25 m. Although such maps of bathymetry are not suitable for navigation, they have many uses in hydrological modelling and describing the physical environment of coral reefs